Having been a former hostile atheist and now a Christian, there is another reason atheists don't want to hear anything about Christianity. An atheist does not have a very stable belief system. An atheist does not want to be reminded that God may actually exist since that is a reminder that they might be wrong. Before becoming a Christian I had to admit that I was really not 100% sure that God did not exist so I had to move to the position of agnostic from the position of atheist. An honest atheist will not claim 100% assurance of God's non-existence. To do so would require 100% knowledge of the world and universe.
Initially, as a smug atheist I made fun of Christians I knew. But they had the confidence I did not have.